224 GEOLOGY OF THE ISLE OF WIGHT. 



to the junction of the greensand with the gait 

 {lign. 17.). 



The Wealden clay, as previously stated, first 

 appears in a bed five or six feet thick, at the foot 

 of Atherfield Point ; the upper layers are shaly, 

 and contain freshwater shells (cyclas, paludina, 

 potamides,* PL VI.) similar to those we observed at 

 Sandown Bay.f The Wealden clay in the upper 

 part is intermixed with grey and green sand ; and 

 two or three inches above there is a stratum of 

 sandy clay containing marine shells. The distance 

 between the layers of fluviatile and marine shells is 

 therefore but a few inches ; so that, as Dr. Fitton 

 remarks, portable masses containing characteristic 

 .shells of both formations may be extracted. I 

 have not been so fortunate as to visit Atherfield 

 Point when the line of junction at the base of the 

 cliff, and to the westward, was exposed to any 

 considerable extent. But sometimes, from a con- 

 junction of favourable circumstances, the strata are 

 laid bare for several hundred yards. This happens 



* Potamides are spiral fresh-water shells, -which much resemble in form 

 those belonging to a marine genus termed Cerithium; the Cerilhia men- 

 tion il by Dr. Fitton as occurring in the Weald clay at Atherfield, may pos- 

 sibly be Potamides. 1 have never observed any vestiges of Cerithia in the 

 Wealden deposits. 



t A few small thin-shelled oysters were observed by Dr. Fitton in this bed. 

 "These fossils occur within a very few inches from the junction with the 

 bovi thi Wealden. " — Proceedings, Geol. Soc. 



